CMOS image sensor capable of increasing fill factor and driving method thereof

Abstract

The present invention relates to a complementary metal-oxide-semiconductor (CMOS) image sensor, comprising: a plurality of unit pixel arrayed in rows and columns, wherein the unit pixel including: (a) a charge generating means for generating charges in response to lights reflected from an object; (b) a first reset transistor for resetting the charge generating means; (c) a floating diffusion region receiving the charges from the charge generating means; and (d) a transfer transistor for receiving an address signal to transfer the charges from the charge generation means to the floating diffusion region; and a plurality of source following unit, each coupled to each column of unit pixel. And also, the present invention provides a driving method the CMOS image sensor.

What is claimed is:  
     
       1. A complementary metal-oxide-semiconductor (CMOS) image sensor, comprising: 
       a plurality of unit pixels arrayed in rows and columns, wherein the unit pixel including:  
       (a) a charge generating means for generating charges in response to lights reflected from an object;  
       (b) a first reset transistor for resetting the charge generating means;  
       (c) a floating diffusion region for forming a capacitor having a capacitance to receive the charges from the charge generating means, wherein the capacitance increases a dynamic range of an output voltage; and  
       (d) a transfer transistor for receiving an address signal to transfer the charges from the charge generating means to the floating diffusion region; and  
       a plurality of source following unit, each coupled to each column of unit pixel.  
     
     
       2. The CMOS image sensor as recited in  1 , wherein the source following unit includes a driver transistor, the driver transistor having: 
       a gate being inputted with an output of the floating diffusion region;  
       a first junction being connected to a power supplying unit; and  
       a second junction being connected an output terminal.  
     
     
       3. The CMOS image sensor as recited in  2 , further comprises a second reset transistor for resetting the floating diffusion region. 
     
     
       4. The CMOS image sensor as recited in  1 , wherein the first reset transistor includes a first junction connected to a power supplying unit and a second junction is connected to the photodiode. 
     
     
       5. The CMOS image sensor as recited in  4 , wherein the second reset transistor includes a first junction connected to a power supplying unit and a second junction is connected to the photodiode. 
     
     
       6. The CMOS image sensor as recited in  4 , wherein gates of the first and second reset transistors are coupled with each other. 
     
     
       7. The CMOS image sensor as recited in  1 , wherein the transfer transistor includes a first junction connected to the charge generating means and a second junction connected to the floating diffusion region. 
     
     
       8. The CMOS image sensor as recited in  claim 2 , wherein source following unit further includes a load transistor having a first junction connected to the second junction of the driver transistor and a second junction ground. 
     
     
       9. The CMOS image sensor as recited in  claim 1 , wherein the charge generating means is a photodiode. 
     
     
       10. A driving method for implementing a complementary metal-oxide-semiconductor (CMOS) image sensor including a photodiode, a floating diffusion region for forming a capacitor having a capacitance to receive the charges from the charge generating means, wherein the capacitance increases a dynamic range of an output voltage, a reset transistor for resetting the photodiode, and a transfer transistor for receiving an address signal and to transfer the charges from the photodiode to the floating diffusion region in a unit pixel, and including a driver transistor in a source following, each coupled to each column of unit pixels, the driving method comprising: 
       turning on the transfer transistor and reset transistor to induce the photodiode into a depletion state, wherein a gate of the transfer transistor receives;  
       turning off the transfer transistor, the reset transistor, and storing an output voltage of the floating diffusion region into a register assigned to each column as reference data through the driver transistor;  
       turning on the transfer transistor, transferring the charges stored at the photodiode to the floating diffusion region and storing variably changing electric potentials of the floating diffusion region into a register assigned to each column as image data through the driver transistor; and  
       displaying actual data obtained from the image data and the reference data.  
     
     
       11. A driving method for implementing a complementary metal-oxide-semiconductor (CMOS) image sensor including a photodiode, a floating diffusion region for forming a capacitor having a capacitance to receive the charges from the charge generating means, wherein the capacitance increases a dynamic range of an output voltage, a first reset transistor for resetting the photodiode, a second reset transistor for resetting the floating diffusion region, and a transfer transistor for receiving an address signal and to transfer the charges from the photodiode to the floating diffusion region in a unit pixel, and including a driver transistor in a source following unit, each coupled to each column of unit pixels, the driving method comprising: 
       turning on the transfer transistor, first reset transistor and the second reset transistor to induce the photodiode into a depletion state, wherein a gate of the transfer transistor receives;  
       turning off the transfer transistor, the first and second reset transistors, and storing an output voltage of the floating diffusion region into a register assigned to each column as reference data through the driver transistor;  
       turning on the transfer transistor, transferring the charges stored at the photodiode to the floating diffusion region and storing variably changing electric potentials of the floating diffusion region into a register assigned to each column as image data through the driver transistor; and  
       displaying actual data obtained from the image data and the reference data.